裂纹尖端运动学揭示脆性水凝胶断裂中的内聚区结构
Crack tip kinematics reveal the cohesive zone structure in brittle hydrogel fracture
AI总结：
本研究利用显微学方法探测脆性水凝胶裂纹尖端的小尺度屈服区，直接测量并确定了通过内聚力丧失耗散大部分能量的区域尺度和结构，为脆性材料破坏机制提供了新见解。
摘要：
当脆性水凝胶发生破坏时，多种机制共同改变裂纹尖端附近的应力状态，识别哪种机制占主导地位极具挑战性。在脆性固体的断裂中，足够的远场应力会导致结构强度完全丧失，因为材料在应力集中的裂纹尖端处发生“解链”。对所谓的小尺度屈服区（变形较大）的直接研究十分稀少。我们以水凝胶作为模型脆性固体，结合多种显微学方法探测了小尺度屈服区，这些方法能够解析变形的运动学。我们在裂纹尖端的紧邻区域识别出一个区域，该区域的大部分能量通过内聚力的丧失而耗散。通过直接测量，我们确定了该区域的尺度和结构，并明确了这种水凝胶材料中特定的能量耗散机制如何推广至脆性材料的破坏。
英文摘要：
When brittle hydrogels fail, several mechanisms conspire to alter the state of stress near the tip of a crack, and it is challenging to identify which mechanism is dominant. In the fracture of brittle solids, a sufficient far-field stress results in the complete loss of structural strength as the material `unzips' at the tip of a crack, where stresses are concentrated. Direct studies of the so-called small-scale yielding zone, where deformation is large, are sparing. Using hydrogels as a model brittle solid, we probe the small-scale yielding region with a combination of microscopy methods that resolve the kinematics of the deformation. A zone over which most of the energy is dissipated through the loss of cohesion is identified in the immediate surroundings of the crack tip. With direct measurements, we determine the scale and structure of this zone, and identify how the specific loss mechanisms in this hydrogel material might generalize for brittle material failure.
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